Recently, the team led by Prof. Yufei Zhao and Associate Prof. Xiao-Jue Bai from Beijing University of Chemical Technology has made significant progress in the field of sustainable nitrogen fertilizer production. Addressing the challenges associated with conventional nitrogen fertilizer manufacturing, including high energy consumption, carbon emissions, and the difficulty of achieving decentralized fertilizer supply, the team developed a novel “plasma activation-paired electrolysis” coupling strategy. This technology enables the direct conversion of air and water into liquid ammonium nitrate fertilizer and demonstrates its potential for direct agricultural applications.
The related work, entitled “Sustainable Synthesis of Ammonium Nitrate From Air and Water via Tandem Plasma-Electrolyzer System,” was published in 《Angewandte Chemie International Edition》. Ph.D. student Qiuhong Sun from Beijing University of Chemical Technology is the first author, while Associate Prof. Xiao-Jue Bai and Prof. Yufei Zhao are the corresponding authors. Beijing University of Chemical Technology is the first affiliation.
Research Background:
Ammonium nitrate (NH4NO3) is an important high-nitrogen fertilizer; however, its conventional production relies on the energy-intensive Haber–Bosch ammonia synthesis and Ostwald oxidation processes, resulting in significant energy consumption and carbon emissions. Moreover, traditional fertilizer application practices often fail to match crop nutrient requirements, leading to excessive greenhouse gas emissions and soil acidification. Therefore, developing a mild-condition route to directly synthesize ammonium nitrate from air, water, and renewable electricity while adapting to plant growth demands represents an important direction for sustainable nitrogen fertilizer production.
Existing photocatalytic and electrocatalytic approaches for atmospheric nitrogen conversion generally suffer from low efficiency and insufficient nitrogen supply capacity for large-scale agricultural applications. Plasma-assisted nitrogen fixation coupled with electrocatalysis provides a promising pathway, where air is first converted into NOx species, followed by absorption and electrochemical conversion to produce gram-scale nitrogen fertilizers, offering the possibility of on-site fertilizer production at farms. However, this strategy still faces several challenges, including the complexity of alkaline absorption processes, sluggish NO3⁻→NO2⁻ conversion kinetics, and the high energy consumption associated with anodic oxygen evolution. Therefore, establishing efficient integration between plasma-generated nitrogen species and downstream electrochemical reactions, enabling continuous production of liquid nitrogen fertilizers directly applicable for plant growth, is crucial for realizing distributed air-to-fertilizer systems and demand-driven precision fertilization.
Key Highlights:
1. Coupling of plasma activation with paired electrolysis
The upstream plasma process converts air into a nitrogen-containing solution dominated by NO2⁻, while the downstream paired electrolysis simultaneously converts NO2⁻ into NH4⁺ at the cathode and NO2⁻ into NO3⁻ at the anode. This design bypasses the sluggish NO3⁻-to-NO2⁻ conversion step and replaces the conventional oxygen evolution reaction with NO2⁻ oxidation, enabling both electrodes to contribute to the synthesis of target nitrogen products.
2. Continuous operation and fertilizer application demonstrate system feasibility
The integrated plasma–paired electrolysis system operates stably for over 210 h at 400 mA cm⁻2, achieving an NH4NO3 production rate of 8.5 mmol h⁻1 per module. The resulting electrolyte can be directly utilized as an N-P-K fertilizer to promote plant growth, demonstrating the potential of a closed-loop pathway from atmospheric nitrogen fixation and ammonium nitrate synthesis to agricultural application.
Figure Analysis:
Figure 1. Comparison of ammonium nitrate synthesis routes and the proposed pNOR-eNO2⁻RR/eNO2⁻OR tandem system developed in this work.
Figure 1 compares four different routes for ammonium nitrate synthesis. The conventional Haber–Bosch/Ostwald processes rely on high-temperature and high-pressure conditions as well as fossil energy inputs. Direct electrochemical N2 reduction/oxidation routes are limited by low N2 conversion efficiency and Faradaic efficiency, while nitrate-based routes using wastewater as feedstock suffer from low nitrate concentrations and high pretreatment costs.
In this work, a point-discharge plasma process is first employed to convert N2 in air into NOₓ species, followed by absorption in 0.5 M phosphate buffer solution to generate a NO2⁻-containing solution. Subsequently, cathodic eNO2⁻RR converts NO2⁻ into NH4⁺, while anodic eNO2⁻OR produces NO3⁻. This integrated design bypasses the sluggish NO3⁻-to-NO2⁻ reduction step and avoids the energy-intensive oxygen evolution reaction as the anodic process, thereby improving nitrogen utilization efficiency at the system level.
Figure 2. Performance, long-term operation, plant growth evaluation, and techno-economic analysis of the pNOR-eNO2⁻RR/eNO2⁻OR continuous-flow system.
After optimizing the cathode catalyst, NO2⁻ oxidation was employed to replace the conventional anodic oxygen evolution reaction, enabling the cathode and anode to selectively produce NH4⁺ and NO3⁻, respectively. The flow electrolyzer maintained an NH4⁺ Faradaic efficiency above 90% at 400 mA cm⁻2, with NH4⁺ and NO3⁻ production rates reaching 9.4 and 10.9 mmol h⁻1, respectively.
By further integrating the point-discharge plasma process with the continuous-flow electrolyzer, the pNOR-eNO2⁻RR/eNO2⁻OR system achieved stable operation for over 210 h, producing approximately 500 mM NH₄NO₃ solution with a single-module production rate of 8.5 mmol h⁻1. Techno-economic analysis demonstrated that this strategy offers promising economic competitiveness by simplifying the process, reducing electrolysis energy consumption, enhancing the value of products generated at both electrodes, and minimizing the transportation and storage costs associated with centralized fertilizer production. The resulting electrolyte can be directly utilized as an N-P-K fertilizer to promote plant growth, highlighting its potential for establishing a closed-loop pathway from atmospheric nitrogen fixation to fertilizer application.
Summary and Outlook:
The major highlight of this work is the development of a renewable electricity-driven “plasma activation-paired electrolysis” coupling strategy. This strategy directly integrates plasma-generated nitrogen species with downstream dual-electrode electrochemical reactions, enabling the simultaneous production of NH4⁺ and NO3⁻ at the cathode and anode, respectively, and achieving the direct conversion of air and water into liquid ammonium nitrate fertilizer. The feasibility of this integrated strategy is further demonstrated through continuous-flow electrolysis, long-term operation over 210 h, plant growth experiments, and techno-economic analysis.
The proposed system features strong potential for modular and distributed deployment, enabling on-site liquid nitrogen fertilizer production near agricultural fields and allowing fertilizer supply to be adjusted according to crop growth stages and nutrient requirements. By reducing the need for centralized fertilizer production, transportation, and storage, this approach provides a more flexible and sustainable pathway for agricultural nitrogen management. In the future, integration with solar photovoltaic power could further establish a renewable-energy-driven “air-water-fertilizer-plant growth” integrated system, offering a new route toward precision fertilization and low-carbon nitrogen management in smart agriculture.
Research Group Introduction:
Associate Professor Xiao-Jue Bai:
Associate Professor Bai Xiao-Jue is a Master's supervisor, with research interests focusing on the controllable synthesis of metal-organic framework (MOF) materials and their catalytic applications. He has led projects supported by the National Natural Science Foundation of China (Young Scientists Fund) and the Chinese Academy of Sciences Special Research Assistant Program, and has participated in strategic priority research programs of the Chinese Academy of Sciences and National Key R&D Programs. He has published more than 30 research articles in journals including Nat. Commun., Angew. Chem. Int. Ed., J. Mater. Chem. A, J. Mater. Chem. C, Chem. Commun., with over 1,000 citations and six granted patents.
Professor Yufei Zhao:
Professor Yufei Zhao is a Professor and Ph.D. supervisor at Beijing University of Chemical Technology. He is the Principal Investigator of the Young Scientist Project under the National Key R&D Program of China, a recipient of the National Science Fund for Excellent Young Scholars, and a member of the China Association for Science and Technology Young Talent Support Program. He has been recognized as a Clarivate Highly Cited Researcher (2019-2024) and an Elsevier Highly Cited Chinese Researcher in Chemical Engineering and Technology (2021-2024), and has been listed among the World’s Top 2% Scientists by Stanford University. His research focuses on the controllable synthesis of hydrotalcite-based nanomaterials and their applications in mineralization and catalysis. He has led multiple national and international research projects and published over 120 SCI papers with more than 27,000 citations (H-index: 82). As the first or corresponding author, he has published more than 80 papers in journals including Chem. Soc. Rev.、J. Am. Chem. Soc.、Angew. Chem. Int. Ed.、Adv. Mater.、Chem、Joule, AIChE J、Chem. Eng. Sci.、Ind. Eng. Chem. Res. and Chem. Eng. J., and has been granted 24 national invention patents. Prof. Zhao is also a co-editor of an RSC English monograph and serves as an editorial board member for several journals, including Acta Physico-Chimica Sinica, Transactions of Tianjin University, SmartMat, and Clean Coal Technology. He has received multiple awards, including the Wiley China High Contribution Author Award (2024), the ACS Industrial & Engineering Chemistry Research Influential Researcher recognition (2023), and the Science and Technology Progress Award from the China Petroleum and Chemical Industry Federation (2022).
Paper Information
Title: Sustainable Synthesis of Ammonium Nitrate From Air and Water via Tandem Plasma-Electrolyzer System
First Author: Qiuhong Sun
Corresponding Authors: Xiao-Jue Bai and Yufei Zhao
Affiliation: Beijing University of Chemical Technology
DOI: 10.1002/anie.3006166